Froth flotation



Unite FROTH FLOTATION Lockwood W. Ferris, Salt Lake City, Utah, assignor to Compania Salitrera Anglo-Lautaro (Anglo-Lantern V Nitrate Corporation), New York, N. Y.

N Drawing. Application November 15, 1952, Serial No. 320,831

Claims. (Cl. 209-166) This invention relates to the separation and separate recovery of water-soluble minerals or inorganic compounds by froth flotation. More particularly, the invention contemplates the provision of an improved multistage process for separating and recovering separately two or more water-soluble mineral components of an original mixture or product involving the treatment by froth flotation in each stage of finely divided, solid particles of the mineral mixture suspended in an aqueous pulp saturated with respect to the component minerals of the mixture to produce in each stage of the process a concentrate of a mineral in the form of a froth and in at least one stage an aqueous suspension of residual minerals, and utilization for the aqueous suspending medium in each stage of the liquid phase of the pulp produced in that stage. The invention further contemplates the provision of an improved multi-stage process or method, involving the use of aqueous suspending mediums and involving the utilization in each stage as the aqueous suspending medium of the liquid phase of the pulp produced in that stage, for treating a product containing or consisting essentially of solid sodium nitrate, solid potassium nitrate and solid magnesium sulphate heptahydrate to produce or obtain (1) a concentrate containing the potassium nitrate in predominant proportion or consisting essentially of potassium nitrate, (2) a concentrate containing the sodium nitrate in predominant proportion or consisting essentially of sodium nitrate and (3) a concentrate containing magnesium sulphate heptahydrate in predominant proportion or consisting essentially of magnesium sulphate heptahydrate.

According to some heretofore customary practices in the selective recovery by froth flotation of two or more water-insoluble minerals from an ore containing such minerals, the ore in the form of an aqueous pulp is subjected in one stage to a froth flotation operation in the presence of reagents that promote the production of a froth concentrate of one mineral while depressing another mineral and inhibiting the production of a froth concentrate containing that mineral. In another stage of the process, the residual pulp containing the minerals depressed in a preceding stage is subjected to a froth flotation operation in the presence of flotation reagents, including activating agents, that promote the production of a froth concentrate containing a mineral depressed in a preceding stage. Such procedures can be carried out satisfactorily in the treatment of ores containingwater-insoluble minerals particularly because the mineral collecting agent employed in one stage is substantially completely adsorbed on the mineral particles collected in the froth concentrate, and, consequently, the residual pulp to be treated in asucceeding stage employing a different mineral collecting agent is not contaminated with a mineral collecting agent employed in' a preceding stage which might interfere-with the production of a suitable froth concentrate in the succeeding'stage.

I have found that in carrying out a froth flotation prdcess forthe selective recovery of different water-solu- 2 ble minerals with the use of diflferent mineral collecting agents in different stages, the mineral collecting agent employed in any stage is not completely adsorbed on the mineral particles collected in the froth concentrate. Some portion of the mineral collecting agent employed in one stage remains in the residual pulp, and it interferes with suspension therein to a flQlgh fiQtfltlOn operation th or inhibits the production of a suitable froth concentrate in a succeeding stage employing a different mineral collecting agent.

Accordingly, flotation operations involving the use of saturated brines or solutions in the treatment of products in the form of mixtures of water-soluble minerals and employing different mineral collecting agents in the dilierent stages, I employ for each stage the liquid phase of the pulp produced in that particular stage in a preceding operation. Of course, in initiating a multiple stage operation, I provide the liquid phase of the flotation pulp for each stage by preparing a solution saturated with respect to the components of the raw or crude mixture of water-soluble minerals from which concentrates of particular minerals are to be obtained. For long periods of time during the course of flotation recovery operations, the initial and, the residual liquid phases of the flotation pulps may be of substantially identical composition in all stages except with respect to flotation reagents contained therein.

Products containing mixtures of such minerals or compounds as potassium nitrate, sodium nitrate and magnejsi um sulphate heptahydrate are typical of mixtures of Watersoluble compounds available and suitable for treatment in accordance With the process of the invention, and the invention, therefore, will he described hereinafter more particularly with respect to processes involving the treatment of such products or mixtures.

Products containing mixtures of solid potassium nitrate, solid sodium nitrate and solid magnesium sulphate heptahydrate may be obtained in one or more stages of proc--- esses involving the recovery by solution and cooling or refrigeration of sodium nitrate from natural sodium ni-' trate-bearing deposits which contain potassium nitrate and magnesium sulphate associated with sodium nitrate.

The process of the present invention permits the separation and separate recovery of sodium nitrate, potassium nitrate and magnesium sulphate heptahydrate contained in pro-'- cipitates'obtained by cooling pregnant solutions thus .pro-

viding for the recovery of three valuable products from a single product having little value as suchf The precipi tated products comprise or consist essentially of solid nitrate, solid particles or" crystals of potassium nitrate and solid particlesor crystals" particles or crystals of sodium of magnesium sulphate heptahydrate.

The method or process of the present invention may be employed to effect separation of the precipitated sodium nitrate, potassium nitrate and magnesium heptahydrate? and provide'concentrateproductsof relatively pureso'di um nitrate,-relatively pure potassium nitrate and relatively pure -magnesium sulphate heptahydrate. A complete separation operation-to increase the purity of a concen trate 'withrespect to its major component may be carried out in a multiple stage operation in which the separate concentrates obtained in any stage may be treated subse quently inaccordanc'e with a process of theinvention.

In accordancewith a method or process of -the invention, (1) a solid product containing sodium nitrate and magnesiumsulphate heptahydrate in large proportion or consisting essentially ofpotassiumnitrate, sodium nitrate and .magnesium sulphate heptahydrateis subjected in the formof an aqueous pulplsaturated with respect to the components of thepreauu'nid; containing solid, finely diyided particles ofthe productp'iri i presence ofan organic cationic flotation reagent which Patented ,Mar. 5,, 1-957:v

in multi-stage, or multiple stage, froth potassium nitrat e,-

functions as a mineral collecting agent to produce a potassium nitrate concentrate in the form of a froth and a concentrate of solid sodium nitrate and solid magnesium sulphate heptahydrate dispersed in finely divided form in the residual flotation pulp; (2) the potassium nitratebearing froth concentrate is separated from the residual flotation pulp; (3) the dispersed solid sodium nitrate and solid magnesium sulphate heptahydrate particles are separated from the liquid phase of the residual pulp, by filtration or otherwise, to obtain a product comprising a mixture of solid particles of sodium nitrate and solid particles of magnesium sulphate heptahydrate; (4) the resulting mixture of solid particles of sodium nitrate and magnesium sulphate heptahydrate in the form of a pulp free of the cationic reagent employed in producing the potassium nitrate concentrate but saturated with respect to the components of the original product comprising potassium nitrate, sodium nitrate and magnesium sulphate heptahydrate and containing the solid particles of the mixture suspended therein is subjected to a froth flotation operation in the presence of a half ester of a saturated monohydroxy alcohol such, for example as sodium lauryl sulphate to produce a sodium nitrate concentrate in the form of a froth and a magnesium sulphate heptahydrate concentrate in the form of solid particles dispersed in the residual flotation pulp; (5) the sodium nitrate-bearing froth concentrate is separated from the residual flotation pulp; and (6) the solid magnesium sulphate heptahydrate particles are separated from the liquid phase of the v residual flotation pulp to produce a solid magnesium sulphate heptahydrate concentrate.

The liquid phases of the residual flotation pulps may be utilized in carrying out additional froth flotation processes of the invention of the types of those of which they are products, or, they may be re-used in processes of the invention designed to improve the grades or qualities of the various concentrates involving re-treatment of the concentrates.

Any suitable organic cationic reagent may be employed as a mineral collecting agent in carrying out a method or process of the invention. Salts of alkylamines may be employed advantageously. In employing a salt of an alkylamine, I prefer to employ a salt in which the alkyl radical contains not less than eight and not more than eighteen carbon atoms. Alkylamine acetates may be employed with advantage. I have employed octadecylamine acetate with particular advantage.

Any suitable half ester of a saturated monohydroxy alcohol may be employed as a mineral collecting agent in a process of the invention for producing the sodium nitrate froth concentrate after separation of the potassium nitrate froth concentrate and after separation of residual solids from the liquid phase of the residual pulp and re-pulping of the residual solids.

For creating or assisting in creating froth at any stage of a process of the invention, I may employ any suitable frothing agent, but I prefer to employ an aliphatic alcohol having frothing properties. Such alcohols include the isomers of hexyl alcohol containing an isometric methyl group. Such isomers may be described as methyl amyl alcohols or as methyl pentanols. The alcohol designated or described as 3-methyl-1-pentanol or a mixture of methyl amyl alcohols containing a substantial proportion of that compound may be employed advantageously.

The product to be subjected to the froth flotation treatment may be ground to produce solid particles of any suitable sizes. Thus, for example, satisfactory results may be obtained by grinding to produce a finely divided product consisting of particles small enough to pass a 48-mesh screen. Grinding to produce a finely divided product consisting essentially of particles small enough to pass a 100-mesh screen, however, results in economy in reagent costs and in a cleaner separation by froth flotation of the components of the original product.

The froth flotation method of the invention may be carried out with a pulp maintained at any suitable temperature. A temperature in the range of about 70 F. to F. (or higher or lower if the atmospheric temperature at the point of location of the operation is higher or lower) may be employed advantageously.

A product of the following composition, typical of precipitates produced in sodium nitrate recovery processes, was treated to demonstrate the effectiveness of the process of the invention:

Component: Percent by weight Sodium nitrate 36.0 Potassium nitrate 39.1 Magnesium sulphate heptahydrate 23.4 Moisture and impurities 1.5

the pebble mill was transferred to a laboratory flotation cell and diluted therein with suiiicient aqueous solution saturated with respect to the components of the product undergoing treatment to produce a pulp containing about twenty-five percent (25%) by weight of suspended solids. The diluted pulp was subjected to a froth flotation treatment in the flotation cell at room temperature in the presence of octadecylamine acetate (CraHsrNHaCHsCOOH) in amount equivalent to eight-tenths (0.8) of a pound per ton of suspended solid particles and methyl amyl alcohol (3-methyl-l-pentanol) in amount equivalent to threetenths (0.3) of a pound per ton of suspended solid partlcles. Agitation of the pulp with the added flotation reagents resulted in the production of a potassium nitrate froth concentrate substantially immediately. The froth produced was skimmed from the surface of the pulp in the flotation cell during a period of about five minutes. The residual pulp was removed from the flotation cell and filtered to separate the liquid and solid phases. The filter cake contained a large proportion of the sodium nitrate and magnesium sulphate heptahydrate of the original product and constituted a concentrate with respect to the sodium nitrate and magnesium sulphate heptahydrate. The filter cake solids were returned to the flotation cell and suspended in an aqueous solution saturated with respect to the components of the original product to form a flotation pulp containing about twenty percent (20%) by Weight of suspended solids. The resulting pulp was subjected to afroth flotation treatment in the flotation cell at room temperature in the presence of sodium lauryl sulphate in amount equivalent to eight-tenths (0.8) of a pound per ton of suspended solids and methyl amyl alcohol (B-methyl-l-pentanol) in amount equivalent to threetenths (0.3) of a pound per ton of suspended solids. Agitation of the pulp with the added flotation reagents resulted in the production of a sodium nitrate-bearing froth concentrate substanially immediately. The froth produced was skimmed from the surface of the pulp during a period of about five minutes. The residual pulp was removed from the flotation cell and filtered to separate the liquid and solid phases. The filter cake contained a large proportion of the magnesium sulphate heptahydrate of the original product and constituted a concentrate of the magnesium sulphate heptahydrate with respect to magnesium sulphate heptahydrate (or a tailing product with respect to sodium nitrate and potassium nitrate).

The following tables show the compositions of the three concentrates and the distribution'of the components of the original product: I

TABLE I Magne: Potas- Sodium sium Percent sium Nitrate, Sulphate byweight Nitrate, percent Heptapercent by weight hydrate, by weight percent by weight Magnesium Sulphate Heptahydrate Concentrate 23. 4 1. 60 3. 9 94. 2 Potassium Nitrate Concenra 40. S1. 00 18.6 0.7 Sodium Nitrate Concentrate. 36. 6 19. 40 77. 4 5.1

TABLE II Distribution (percent by weight) Potassium Sodium Magnesium Nitrate Nitrate Sulphate Heptahydrate Magnesium Sulphate Heptahydrate Concentrate... 0. 9 2. 4 94. 2 Potassium Nitrate Concentrate 81. 3 20. 3 O. 7 Sodium Nitrate Concentrate 17. 8 77. 3 5.1

The above-described operation was repeated ten times (carried out eleven times) with the liquid phase of the residual pulp of each step or stage being employed as the liquid vehicle in forming the flotation pulp for that particular step or stage. The results obtained were consistent throughout the tests carried out repeatedly.

Data concerning the first test or operation are set forth in Tables I and II above. The following tables show the compositions of the three concentrates and the distribution of the components of the original product for the eleventh (11th) test.

TABLE III Magne- Potas- Sodium sium Percent sium Nitrate, Sulphate by weight Nitrate, percent Heptapercent by Weight hydrate, by weight percent by weight Magnesium Sulphate Heptahydrate Concentrate 23. 3 0.26 1. 06 95. 8 Potassium Nitrate Concentrate 45. 0 74. 50 22. 50 l. 7 Sodium Nitrate Concentrate 31. 7 11. 10 S2. 20 7 TABLE IV Distribution (percent by weight) Potassium Sodium Magnesium Nitrate N itrate Sulphate Heptahydmtc Magnesium Sulphate Heptahydrate Concentrate... 0.2 2.8 90. 0 Potassium Nitrate Concentrate 90. 3 26. 8 3. 0 Sodium Nitrate Concentrate 9. 70. 4 7. 0

I claim:

1. The method of separating and separately recovering two or more mineral components of an original mixture of two or more solid water-soluble mineral components which comprises (1) subjecting the mixture in the form of an aqueous pulp saturated with respect to the comselective froth flotation operation capable ofprodiicing.

a concentrate of a mineral in the form of a froth and a residual pulp containing in suspension in the liquid phase of the pulp solid particles of residual minerals, (2) separating and recovering the froth concentrate, (3) separating the residual mineral particles from the liquid phase of the residual pulp, (4) subjecting the separated residual mineral particles in the form of a pulp saturated with respect to the components of the original mixture of minerals to a selective froth flotation operation capable of producing a concentrate of another mineral in the form of a froth and a residual pulp having in suspension therein solid particles of one or more additional minerals, (5) separating and recovering the froth concentrate, (6) separating the one or more additional minerals from the liquid phase of the residual pulp associated therewith, and (7) utilizing the separated liquid phases of the residual pulps repeatedly in forming pulps in the particular selective froth flotation operations of which they are products.

2. The method of separating and separately recovering potassium nitrate, sodium nitrate and magnesium sulphate heptahydrate contained in a solid product consisting largely of potassium nitrate, sodium nitrate and magnesium sulphate heptahydrate which comprises, initially, (1) subjecting the product in the form of an aqueous pulp saturated with respect to the components of the product and containing finely divided, solid particles of the product suspended therein to a selective froth flotation operation in the presence of a salt of an alkylamine to produce a potassium nitrate concentrate in the form of a froth and a residual pulp containing a concentrate comprising solid particles of sodium nitrate and solid particles of magnesium heptahydrate dispersed therein, (2) separating and recovering the potassium nitrate concentrate from the residual flotation pulp, (3) separating and recovering the dispersed solid sodium nitrate and solid sodium sulphate heptahydrate concentrate from the liquid phase of the residual pulp, (4), initially, subjecting the solid sodium nitrate and solid magnesium sulphate heptahydrate in the form of a pulp saturated with respect to the components of the original solid product and containing the solid particles of sodium nitrate and magnesium sulphate heptahydrate suspended therein to a selective froth flotation operation in the presence of sodium lauryl sulphate to produce a sodium nitrate concentrate in the form of a froth and a residual pulp having solid particles of magnesium sulphate heptahydrate, (5) separating and recovering the sodium nitrate concentrate from the residual pulp, 6) separating the mag nesium sulphate heptahydrate from the liquid phase of the residual pulp associated therewith, and (7) utilizing the separated liquid phases of the residual pulps repeatedly in forming pulps in the particular selective froth flotation operations of which they are products.

3. The method as defined in claim 2 wherein the salt of an alkylamine is one wherein the alkyl group contains not less than eight nor more than eighteen carbon atoms.

4. The method as defined in claim 2 wherein the salt of an alkylamine is an octadecylamine salt.

5. The method as defined in claim 2 wherein the salt of an alkylamine is octadecylamine acetate.

References Cited in the file of this patent UNITED STATES PATENTS 2,120,217 Harris June 7, 1938 2,222,330 Weinig Nov. 19, 1940 2,297,664 Tartaron Sept. 29, 1942 2,469,422 Weinig May 10, 1949 (Other references on following page) 7 55 OTHER REFERENCES Chemiker Zeituqg, March 1, 1939, No. 17, pages 148- T a1 D ha i 149. Translation 1n Div. 55. 9 pages. & i ggg z fig. :353. g Russian Patent 47,678, Extract translatlon from Report of the Committee on Inventions (Vestnik komiteta 5 p0 izolretatel stvu), No. 7, July 31, 1936, in Division 55, Soluble Salts, 1 page.

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2. THE METHOD OF SEPARATING AND SEPARATELY RECOVERING POTASSIUM NITRATE, SODIUM NITRATE AND MAGNESIUM SULPHATE HEPTAHYDRATE CONTAINED IN A SOLID PRODUCT COSISTING LARGELY OF POTASSIUM NITRATE, SODIUM NITRATE AND MAGNESIUM SULPHATE HEPTAHYDRATE WHICH COMPRISES, INITIALLY (1) SUBJECTING THE PRODUCT IN THE FORM OF AN AQUEOUS PULP SATURATED WITH RESPECT TO THE COMPONENTS OF THE PRODUCT AND CONTAINING FINELY DIVIDED, SOLID PARTICLES OF THE PRODUCT SUSPENDED THEREIN TO A SELECTIVE FORTH FLOTATION OPERATION IN THE PRESENCE OF A SALT OF AN ALKYLAMINE TO PRODUCE A POTASSIUM NITRATE CONCENTRATE IN THE FORM OF A FROTH AND A RESIDUAL PULP CONTAINING A CONCENTRATE COMPRISING SOLID PARTICLES OF SODIUM NITRATE AND SOLID PARTICLES OF MAGNESIUM HEPTAHYDRATE DISPERSED THEREIN, (2) SEPARATING AND RECOVERING THE POTASSIUM NITRATE CONCENTRATE FROM THE RESIDUAL FLOTATION PULP, (3) SEPARATING AND RECOVERING THE DISPERSED SOLID SODIUM NITRATE AND SOLID SODIUM SULPHATE HEPTAHYDRATE CONCENTRATE FROM THE LIQUID PHASE OF THE RESIDUAL PULP, (4), INITIALLY, SUBJECTING THE SOLID SODIUM NITRATE AND SOLID MAGNESIUM SULPHATE HEPTANYDRATE IN THE FORM OF A PULP SATURATED WITH RESPECT TO THE COMPONENTS OF THE ORIGINAL SOLID PRODUCT AND CONTAINING THE SOLID PARTICLES OF SODIUM NITRATE AND MAGNESIUM SULPHATE HEPTAHYDRATE SUSPENDED THEREIN TO A SELECTIVE FROTH FLOTATION OPERATION IN THE PRESENCE OF SODIUM LAURYL SULPHATE TO PRODUCE A SODIUM NITRATE CONCENTRATE IN THE FROM OF A FROTH AND A RESIDUAL PULP HAVING SOLID PARTICLES OF MAGNESIUM SULPHATE HEPTAHYDRATE, (5) SEPARATING AND RECOVERING THE SODIUM NITRATE CONCENTRATE FROM THE RESIDUAL PULP, (6) SEPARATING THE MAGNESIUM SULPHATE HEPTAHYDRATE FROM THE LIQUID PHASE OF THE RESIDUAL PULP ASSOCIATED THEREWITH, AND (7) UTILIZING THE SEPARATED LIQUID PHASES OF THE RESIDUAL PULPS REPEATEDLY IN FORMING PULPS IN THE PARTICULAR SELECTIVE FROTH FLOTATION OPERATIONS OF WHICH THEY ARE PRODUCTS. 